The present invention relates to a system and method for controlling fuel injection in an automotive engine having a single point injector, and more particularly to the system and method for controlling the quantity of fuel to be injected in accordance with a transport model of the fuel.
In a fuel injection system provided with a single fuel injector in a throttle body provided in an intake passage, injected fuel is induced in cylinders of the engine through the intake passage. A part of the fuel passing through the intake passage adheres to the wall of the passage to form a fuel film thereon. The fuel adhered to the wall eventually evaporates and is induced in the cylinders together with the injected fuel, which causes a difference between the quantity of the injected fuel calculated in dependency on engine operating conditions and the quantity actually induced in the cylinders of the engine. In order to control the actual quantity induced in the cylinders to a desired quantity, a fuel injection system has been proposed where the amount of fuel adhered to the wall of the intake passage and the rate of evaporating fuel thereof are estimated based on the fuel transport model to correct the quantity of fuel to be injected. Japanese Patent Laid-Open No. 61-126337 discloses a fuel injection system where a fuel injection quantity Gf is calculated based on a desired fuel quantity Qa/(A/F), a quantity of evaporated fuel Mf/.tau., a rate (1-x) of the quantity of fuel induced into the cylinders of the engine without adhering to the wall of the intake passage.
The prior art discloses a system for providing only a basic fuel injection quantity. Since there are various noise sources such as a spark plug in an engine compartment, the output signals of various sensors such as an engine speed sensor and a throttle position sensor can be affected by the noises. Consequently, the fuel injection quantity which is calculated based on engine speed and a throttle position is miscalculated, and hence, in particular in an engine with a single point injector, the fuel injection quantity oscillates, which causes deterioration of emission control and driveability.
To solve such a problem, the calculated fuel injection quantity should be filtered, for example by performing a weighted mean method. However, if a weight is constant regardless of the engine operating condition, the response of the engine speed in a transient state is delayed.